Manufacture of armor-plates.



UNITED STATES ATENT @FFICE.

MANUFACTURE OF ARMOR-PLATES.

Specification of Letters Patent.

Patented Sept. 25, 1906.

Application filed October 18,1905. Serial No. 283,235.

To all whom, it may concern.-

Be it known that 1, ROBERT A. HADFIELD, a subject of the King of Great Britain, and a resident of Sheflield, county of York, England, have invented'an Improvement in the Manufacture of Armor-Plates, of which the following description is a specification.

Armor-plates are now commonly made of steel by rolling with plain flat surfaces 'and subsequently hardening the face by com entation, and, as is well known, such plates are not only costly to produce, but they can be readily perforated with capped projectiles.

In the course of my experiments to decrease the cost of production of armor-plate I and to increase the resistance thereof to'penetration I have-discovered that the desired results canbe obtained. by casting suitable steel in a suitable mold and subsequently hardening the face by ap ropri'ate treatment. Armor-plate so producecfofiers such great resistanceto. penetration as to largely, if not entirely, neutralize the fprotective action of the cap on a projectile-o the type commonly used for perforating ordinary Krupp cementbe steel prepared similarly to the manner-set forth in my British Patent No. 16,132 of 1901.- After pouring and while the casting is hot it is removed to a furnace to cool down slowly, and thereby prevent it being strained internally, after which the sand is removed and the casting carefullycleaned. The casting is now placed in al'urnace, and upon the face of the casting is placed charcoal, forming a layer several inches thick, and the temperature of the furnace is raised to, say, between 900 and l,100 centigrade and so maintained for several days, after which it is allowed to gradually cool down. The head or riser is then removed in suitable manner, and the late is'heated to from 700 to 800 centigra e, preferably about 730 Centigrade,

invention I prepare a and cooled slowly in the furnace, this heating being then repeated, with subsequent cooling to about 640 centigrade, and quenching. The quenched plate is new again heated to 620 centigrade, or thereabout, and uenched, after which the plate is thenuni ormly or taper heated. In the latter case the plate is so heated that its face assumes a tempera ture of from 700 to 7 centigrade, taper ing or decreasing to about 400 or 500 at the back. I then heat the plate in a similar manner to that described in my British Pat.- ent' No. 15,220 of 1904a; asufiiciently high temperature so that being somewhat hotter when dipped orsprayed with oil or water, according to the hardness required, the face of the plate becomes hard and the back. remains soft and tough,

Preferably the plate is subjected to the entire process or treatment described in said patent.

I may more or less modify the details'oftreatment hereinbefore setforth without departing from my invention. In some cases,-

for instance, if a very softsteel is usedt. a, low in carbon-a uniform heating may be adopted instead of a taperheating.

Having fully described my invention, what I claim as new, and desire to/secure by Letters Patent, is-

1. The process of making steel armorplate, comprising the steps of casting the plate, subjecting the plate to a temperature up to 1,100 centigrade while the facethereof is in contact with carbonaceous material,

gradually cooling down the plate, and then reheating the plate to a lower temperature;

subsequently quenching at' about 640 centigrade; and finally heating to a hardening 3; The process of making steer armorplate, which consists in casting the plate; slowly cooling and cleaning the casting; covering its face with charcoal and sub ectmg the plate for several days to a temperature of from 000 centigrade to 1 ,100centigrarle and finally treating theplate so that when dipped allowing it to gradually cool down; heating or sprayed with oil or water the face becomes to from 700 to 800 centigrade and cooling I hard and the back remains soft and tough. it slowly in a furnace; repeating the last In testimony whereof I have signed my 5 heating, cooling to about 640 Centigrade and g name to this specification in the presence of 15 quenching; reheating to about 620 centii two subscribing witnesses. grade and again quenching; finally heating R. A. HADF IELD. the casting to a temperature of from 700 to Witnesses: 750 centigralle at its face and tapering to l r G. H.HEMSOLL, 10 from 400 to 500 centigrade at its back vancl J. W. CRAWLEY.. 

